Conventionally, large commercial aircraft, also referred to as airplanes hereinafter, use their gas turbine engines to taxi on an airfield or maneuvering area of an airport. As the gas turbine engines of airplanes are not designed to operate efficiently in a low power state, such as needed during the taxiing operation on the ground, maneuvering of the aircraft on the ground consumes a lot of fuel. Increasing fuel prices have made this fuel consumption during taxiing more and more worrisome. Moreover, the fuel efficiency for the whole flight decreases due to the large amount of fuel that has to be carried during the flight for taxiing at the destination airport. Alternatively, special vehicles are used to drag or push airplanes on an airfield. However, since such special vehicles are expensive themselves and not available in large numbers at most airports, they are commonly only used for short distances, such as the push-back operation from the gate. This again leads to the gas turbine engines being used for most of the taxiing, which causes above described disadvantages.
Alternative solutions for taxiing of aircraft have been suggested in the prior art. DE10 2008 006 295 A1 discloses an electric motor mounted onto a running gear leg of an aircraft. The electric motor comprises a motor shaft, which can be moved axially between different positions in order to engage/disengage with the wheel structure of the aircraft running gear and drive the wheel.
Although improvements could be achieved with such approaches, it has been found that—especially for large commercial aircraft—these approaches did not yield satisfying results in terms of durability/service life, when attempting to supply the necessary power to drive the aircraft without the help of the turbine engines.